Many drugs are now available to be used in the treatment of cancer. However, in many cases the cancer fails to respond to the anti-cancer therapy or its growth and/or metastasis is only slowed. Even when a tumor initially responds to an anti-cancer therapy by decreasing in size or going into remission, the tumor often develops resistance to the drug. For these reasons, there has been a need for new anti-cancer agents and for new drugs which can be used to treat multi-drug resistance cancers.
Certain bis(thio-hydrazide amide) compounds have been described by the present inventors as being significantly cytotoxic to cancer cells, including cancer cells that have become multi-drug resistant, and for enhancing the anti-cancer activity of other anti-cancer agents, such as paclitaxel and Epothilone D (see, e.g., U.S. Publication Nos. 2004/0225016 A1, 2003/0045518 and 2003/0119914, the entire contents of which are incorporated herein by reference).